1. Field of the Invention
The invention relates to a semiconductor device and more particularly to several types of metal oxide semiconductor field transistors.
2. Description of Related Art
Ultra high voltage devices must have high breakdown voltage and low on-state resistance (Ron) during operation to reduce power loss. To provide higher current and maintain sufficient breakdown voltage, array structures are now developed. In layouts of alternating current-direct current electronic products, layout areas can be decreased and the performance of devices can be enhanced through the array structures. In an ultra high voltage device currently developed, a source region and a drain region thereof have a shape of interdigitated fingers. Although a source terminal and a drain terminal having the shape of interdigitated fingers can decrease the layout area, a curvature thereof is large. A large current is particularly accumulated at the source terminal which becomes a breakdown point, thereby resulting in the decrease of the breakdown voltage of the device.